# NTSB WPR24LA093: Bell 47G-3B-1, N2618W, Garey, CA, February 23, 2024 - Type: NTSB accident investigation - Classification: Accident · Minor injuries · Class 3 · Limited · Final report - Date: February 23, 2024, 07:40 local (15:40 UTC) - Place: Garey, CA - Coordinates: 34.894958, -120.32216 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=34.8950&lon=-120.3222&mi=10 - Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping) - Defining event: [Maneuvering-low-alt flying: Loss of engine power (total)](https://openairdocs.org/ntsb-events/341) - Highest injury: Minor injuries - Injuries: 1 minor - Status: Completed - Report: Approved by Office Director - Investigation class: Class 3 - NTSB office: Western Pacific Region - Parties: Federal Aviation Administration, Rolls-Royce - NTSB case key (mKey): 193831 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=WPR24LA093 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/193831/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=193831 - Page: https://openairdocs.org/ntsb/WPR24LA093 ## Probable cause Maintenance personnel’s failure to properly check the torque paint on a fuel control unit B-nut, which resulted in the loosening of the B-nut, a loss of engine power at a low altitude, and a subsequent impact with terrain. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Engine fuel and control: fuel control/carburetor](https://openairdocs.org/ntsb-findings/01057322): Aircraft › Aircraft power plant · Incorrect service/maintenance (probable cause); cases with it: [Bell 47G-3B-1, 1 case](https://openairdocs.org/ntsb-findings/01057322/cases.md?model=1181028), [All aircraft, 195 cases](https://openairdocs.org/ntsb-findings/01057322/cases.md) - [Aircraft capability: climb capability](https://openairdocs.org/ntsb-findings/01061010): Aircraft › Aircraft oper/perf/capability · Attain/maintain not possible; cases with it: [Bell 47G-3B-1, 1 case](https://openairdocs.org/ntsb-findings/01061010/cases.md?model=1181028), [All aircraft, 183 cases](https://openairdocs.org/ntsb-findings/01061010/cases.md) - [Maintenance: scheduled/routine maintenance](https://openairdocs.org/ntsb-findings/02062010): Personnel issues › Task performance · Maintenance personnel (probable cause); cases with it: [Bell 47G-3B-1, 1 case](https://openairdocs.org/ntsb-findings/02062010/cases.md?model=1181028), [All aircraft, 320 cases](https://openairdocs.org/ntsb-findings/02062010/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Maneuvering-low-alt flying: Loss of engine power (total)](https://openairdocs.org/ntsb-events/341) (defining event); cases with it: [Bell 47G-3B-1, 5 cases](https://openairdocs.org/ntsb-events/341/sequence.md?model=1181028), [All aircraft, 3,820 cases](https://openairdocs.org/ntsb-events/341/sequence.md) ## Analysis The pilot of the helicopter was applying a chemical to a field when the engine sustained a loss of power. The pilot entered an autorotation and the helicopter descended to the terrain, where it rolled onto its right side substantially damaging the main rotor system and severing the tailboom. Postaccident examination of the pneumatic air lines revealed that there was a slight air leak at the accumulator and a large air leak at a pneumatic air line (Pc) between the power turbine governor (PTG) and the fuel control unit (FCU); the Pc line was not connected to the FCU. The B-nut connecting the Pc line to the FCU had backed off, allowing the Pc line to become disconnected. . This Pc line is one of several lines that use air pressure to communicate fuel scheduling commands between the PTG and the FCU. The security of this line is necessary for proper engine operation. Engine operation without the Pc line properly connected would result in the FCU reducing fuel to a sub-idle condition, preventing the engine from producing sufficient power for continued flight. No other preaccident mechanical malfunctions or failures were found that would have precluded normal operation. Maintenance was performed on the helicopter 15 days and 29.2 flight hours before the accident that included checking all B-nuts for torque paint to ensure adequate torque remained on the B-nuts. Maintenance personnel likely did not properly inspect the condition of the torque paint on the affected B-nut, which resulted in a disconnection of the B-nut from the FCU and a total loss of engine power. ## Factual narrative On February 23, 2024, about 0740 Pacific standard time, a Bell 47G-3B-1, N2618W, was substantially damaged when it was involved in an accident near Garey, California. The pilot received minor injuries. The helicopter was operated as a Title 14 Code of Federal Regulations Part 137 aerial application flight. According to the pilot, he was about 5 ft above ground level (agl) at an airspeed of 40 knots conducting an aerial application of fungicide on a field when he then initiated a climb to clear a set of power lines. As he increased power for the climb, he noticed the engine out/low rotor audible warning and the engine simultaneously exhibited a loss of power. He performed an autorotation to an off-airport site. During the autorotation the helicopter entered an uncommanded roll to the left. Despite his control inputs, the pilot was unable to arrest the roll and the helicopter impacted terrain in a nose-down, left-side-low attitude. The helicopter came to rest on its right side with substantial damage to the tailboom and main rotor system. Postaccident examination of the airframe revealed the fuselage exhibited impact damage to the right side. The right skid fractured at the struts and separated from the fuselage. The bubble canopy fractured and separated from the fuselage. The tailboom exhibited a fracture and separation consistent with impact from the main rotor blades. Postaccident examination revealed the engine remained secured to the airframe by the mounts. Manual rotation of the main engine driveshaft resulted in the rotation of the stage four turbine wheel, confirming continuity of the N2 drivetrain. Motoring the engine by the starter generator resulted in smooth rotation of the compressor rotor, confirming continuity of the N1 drivetrain. Engine control continuity was confirmed from the throttle to the fuel control unit. All engine oil and fuel lines were found secured with all B-nuts being at least hand tight and with no evidence of leakage. A check of the pneumatic system by application of about 25 psi of air pressure at the Pc filter resulted in the detection of minor air leakage at both B-nuts on both ends of the accumulator and a large leak at the PTG to FCU Pc input line. Closer examination revealed the B-nut had no thread engagement and had slid aft down the Pc line, as shown in figure 1. The input union on the FCU exhibited evidence of green colored torque paint that was similar in color to the other B-nuts and inputs on the FCU. Figure 1. Image of the accident fuel control, showing the B-nut, the flared end of the Pc line, and the threads of the attachment fitting of the fuel control. According to Rolls-Royce, the engine manufacturer, the Pc line connecting the PTG to the FCU is the third of three Pc lines in the system. Pc air is the power supply or motive force that allows the fuel control to modulate fuel delivered to the engine fuel nozzle. With this line disconnected, the engine would reduce power to an unpowered static-stateor sub-idle condition. Further examination of the fuel control, fuel governor, and fuel nozzle revealed normal operation. No other preaccident mechanical malfunctions or failures with the engine or airframe were found that would have precluded normal operation. According to maintenance records, on June 23, 2023, the fuel control was installed on the accident engine along with several other engine components, including the fuel pump, governor, fuel nozzle, bleed control assembly, and a tachometer generator. On February 8, 2024, about 15 days before the accident, at a Hobbs time of 902.5, a maintenance facility completed the 150-hour/300-hour engine inspections, along with several airframe inspections. According to the Rolls-Royce Alternate Inspection Schedule, the 150/300-hour inspection states, in part, “Inspect all B-nuts for application and alignment of torque paint. If missing, loosen the B-nut, retighten, and apply torque paint.” The Hobbs meter at the time of the accident read 931.7. The maintenance technician who signed off the work did not recall the specifics of the annual inspection conducted on February 8, 2024, as he did several inspections during the shift, but did report the use of the checklists for each inspection. Rolls-Royce released commercial service letter (CSL) 2373 that addressed a special tool to access the subject B-nut. The CSL provides details on how to manufacture the tool locally and the tool is also available for purchase. ## Aircraft - Registration: [N2618W](https://openairdocs.org/aircraft/N2618W), registered now, S/N 6580, built 1966 (OpenAirDocs) - Reported make and model: BELL 47G-3B-1 - Registry model: [Bell 47G-3B-1](https://openairdocs.org/model/bell-47g-3b-1) (registry code 1181028) (OpenAirDocs) - Registry engine: [Allison 250 series](https://openairdocs.org/engine/allison-250-series) (registry code 03014, turbo-prop) (OpenAirDocs) - Category: Helicopter - Serial number: 6580 - Year built: 1966 - Airframe hours: 12450.7 - Engines: Rolls-Royce 250 SERIES 420 horsepower turbo shaft - Damage: Substantial damage - Flight: Aerial application, Part 137 - Operator: English Air Service LLC - Registered owner: English Air Service LLC - Airworthiness certificate: Special, Restricted (Special) - Last inspection: Annual, February 8, 2024 - Departed: SMX, Santa Maria, CA - Flight plan: Company VFR - Airport: SMX, Santa Maria - Equipment: None ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 63; injuries: minor; commercial; instrument ratings: helicopter; medical: class 2, with waivers/limitations; last flight review April 2, 2022; seat: left; restraint: 4-point; flight hours: 15,000 total, 15,000 in this make and model ## Weather - Conditions: Visual (VMC), Day - Wind: calm - Visibility: 9 statute miles - Lowest ceiling: 20,000 ft broken - Temperature: 46 °F, dew point 45 °F - Altimeter: 30.08 inHg - Observed at: KSMX, 6 nm away - METAR: KSMX 231551Z 00000KT 9SM BKN200 08/07 A3008 RMK AO2 SLP191 T00780072 ## FAA reports on this event (1) The FAA's own accident and incident reports, matched to the aircraft by N-number and date (OpenAirDocs). - [Accident 20240223000789A](https://openairdocs.org/incident/20240223000789A), Feb 23, 2024: Bell 47G-3B-1, Garey, CA, Destroyed. The pilot was performing aerial application over a broccoli field in Garey California when he initiated a climb to 80 feet (AGL) to overfly power lines. As the… ## Docket (8 files) The files NTSB released with the investigation on July 23, 2025, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=193831. 15.2 MB in all. - Pilot/operator aircraft accident report, NTSB form 6120.1 (item 1, PDF, 10 pages, 3.0 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16960565&FileExtension=pdf&FileName=NTSB%206120.1_N2618W_DeanTuck_Redacted-Rel.pdf - Photos (item 2, PDF, 5 pages, 2.4 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18348400&FileExtension=pdf&FileName=Photos%20for%20WPR24LA093_Redacted-Rel.pdf - Airframe and engine examination report (item 3, PDF, 25 pages, 3.7 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18473296&FileExtension=pdf&FileName=A%26E%20Exam%20Report%20for%20WPR24LA093_Redacted-Rel.pdf - Engine examination report rolls-royce (item 4, PDF, 14 pages, 2.4 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18505697&FileExtension=pdf&FileName=English%20Air%20Service%20Engine%20Exam%20Update%20Rev%201_Redacted-Rel.pdf - Fuel control maintenance sheet (item 5, PDF, 1 page, 913 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18349780&FileExtension=pdf&FileName=Fuel%20Control%20Maintenance%20Sheet-Rel.pdf - Reports from parties to the investigation (item 6, PDF, 11 pages, 2.4 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18667813&FileExtension=pdf&FileName=English%20Air%20Service%20Engine%20Exam%20Update%20Rev%201_Redacted-Rel.pdf - Mechanics statement (item 7, PDF, 1 page, 81 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18667803&FileExtension=pdf&FileName=Maintenance%20Responce_Redacted-Rel.pdf - Party member certificate (item 8, PDF, 1 page, 195 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16960642&FileExtension=pdf&FileName=Party%20Member%20Certificate%20WPR24LA093_Garey_CA_Redacted-Rel.pdf From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model. --- OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.